The primate prefrontal cortex plays a central role in the perception of sensory information and the planning of intelligent behavior, evidenced by the profound cognitive deficits following prefrontal injury and the mental illnesses associated with prefrontal malfunction. Previous neurophysiological studies in primates have sought to understand the involvement of the prefrontal cortex in cognitive functions and have indeed revealed prefrontal activation during execution of a large variety of behavioral tasks. Much less is known, however, on how the prefrontal cortex operates under more natural conditions, before animals have been heavily conditioned to perform a stereotypical task, and how training itself modifies neuronal responses and neural circuitry. In fact, the fundamental organization of sensory information within the prefrontal cortex has been under debate, as training in different tasks has resulted in quite distinct patterns of prefrontal activation. We have recently initiated a series of experiments examining the principles of prefrontal intrinsic connectivity as well as experiments examining neuronal responses of monkeys naive to behavioral training. Taking advantage of the methodological advancements and preliminary findings of these studies, we propose to test the nature of prefrontal encoding of visual information before and after training. Experiments will first test whether neurons in the dorsolateral and ventrolateral prefrontal cortex encode the spatial locations and features of visual stimuli presented passively and having no significance for the monkeys. The same monkeys will subsequently be trained in cognitive tasks that require them to identify and remember the spatial locations and features of these stimuli, allowing us to test whether single neurons are able to integrate spatial and feature information after training. We will use microelectrode arrays to record neural and to determine changes in the patterns of neuronal activation and in the functional connectivity between neurons. In the last few years, training human patients in similar tasks has emerged as a means of restoring cognitive function compromised after traumatic brain injury or stroke and ameliorating the effects of genetic brain disorders. Our results will shed light on the underlying neural circuit changes following cognitive training and offer insights on the design of better intervention strategies for the remediation of these conditions.